Liquid crystal display panel and repairing method thereof

ABSTRACT

A method of repairing a defect in a liquid crystal display panel is provided. The method comprises: providing an array substrate, a plurality of pixel regions over the array substrate, and at least one of the pixel regions comprising a transistor, a pixel electrode, a storage capacitor having an upper electrode and a bottom electrode, a defect positioned in the storage capacitor; performing a cutting process to divide the pixel electrode into a first portion and a second portion not connecting to each other, wherein said first portion of said pixel electrode is corresponding to the storage capacitor having said defect; and electrically connecting the second portion of the pixel electrode to one of the scan lines.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display panel andrepairing method thereof, and more particularly, to a method able torepair bright dot defect or other pixel defect problem in an arraysubstrate of a liquid crystal display panel.

2. Description of the Prior Art

A conventional liquid crystal display (LCD) panel normally includes athin film transistor array substrate (array substrate), a color filtersubstrate (CF substrate) having a common electrode thereon disposed overthe array substrate, and a liquid crystal layer interposed therebetween. Please refer to FIGS. 1-2. FIGS. 1-2 are schematic diagramsillustrating an array substrate of a conventional LCD panel, where FIG.1 is a top view of a portion of the array substrate, and FIG. 2 is across-sectional view of the array substrate shown in FIG. 1 along theline PP′. As shown in FIG. 1-2, the conventional array substrate 10includes a plurality of scan lines 12, a plurality of data lines 14, aplurality of pixel regions 16 defined by the scan lines 12 and the datalines 14, and a plurality of common lines 20 arranged in alternatelywith the scan lines 12. Each pixel region 16 has at least a thin filmtransistor 18 and a pixel electrode 22 corresponding to the thin filmtransistor 18. The pixel electrode 22 is disposed facing the commonelectrode of the CF substrate (not shown), in which the liquid crystalis interposed between the pixel electrode 22 and the common electrode.In addition, the overlapping region of the pixel electrode 22 and thecommon line 20 form a storage capacitor on common line (Cst on common).Each thin film transistor 18 serves as a switch in each pixel region 16.In the displaying operation, the common electrode of the CF substrate isusually receiving a common voltage. Following, a particular pixel regionis selected through a corresponding scan line 12 receiving a scan signaland then the pixel electrode 22 of the pixel region 16 is written into apixel voltage via a corresponding data line 14 receiving a data signal.Sequentially, the voltage difference between the pixel electrode 16 andcommon electrode makes the liquid crystal rotate to a predetermineddirection to control the illumination out from the CF substrate and thena display is achieved.

The storage capacitor assists the pixel region 16 to operate normally,however, any processing defects or particles occurring in the storagecapacitor may lead to malfunction of the storage capacitor. Forinstance, if a particle 24 unexpectedly falls into the storage capacitorregion, the particle 24 may lead to a short-circuitry between the pixelelectrode 22 and the common line 20. In such a case, the voltage of thepixel electrode 22 will be identical to the voltage of the common line20. Since the common line 20 and the common electrode of the CFsubstrate usually have the same voltage, the voltage of the pixelelectrode 22 and the voltage of the common electrode of the CF substratewill be identical. This fails the pixel region 16. Furthermore, if theLCD is a normally white (NW) type LCD, back light will pass through theliquid crystal layer and cause a bright dot defect because no voltagedifference exists between the pixel electrode 22 and the commonelectrode. In addition to the particles, other defects such as adielectric layer loss or a common line loss that makes the pixelelectrode 22 and the common line 20 short-circuited will also cause thebright dot defect in an NW type LCD.

Accordingly, there is a need to provide a simply and effective repairingmethod of the pixel to solve the display problems due to particles orother defects.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a liquid crystaldisplay and repairing method thereof to solve the bright dot defect andother pixel defect problem.

It is another objective of the present invention to provide a liquidcrystal display and repairing method which is easy to be implemented inthe manufacture process.

According to an embodiment of the present invention, a method ofrepairing a defect in a liquid crystal display panel is provided. Themethod comprises: providing an array substrate comprising a plurality ofscan lines and data lines disposed over the array substrate and togetherdefining a plurality of pixel regions, and at least one of the pixelregions comprising a transistor, a pixel electrode electricallyconnected to a source/drain electrode of the transistor, a storagecapacitor having an upper electrode and a bottom electrode, wherein thepixel electrode is electrically coupled to the storage capacitor, andthere is a defect positioned in the storage capacitor; subsequently,performing a cutting process to divide the pixel electrode into a firstportion and a second portion not connecting to each other, wherein thefirst portion of the pixel electrode is corresponding to the storagecapacitor having the defect; and then electrically connecting the secondportion of the pixel electrode to one of the scan lines.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-2 are schematic diagrams illustrating a conventional arraysubstrate.

FIGS. 3-8 are schematic diagrams illustrating a method of repairing adefect in an array substrate of an LCD panel in accordance with thefirst embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating a method of repairing adefect in an array substrate of an LCD panel in accordance with thesecond embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a method of repairing adefect in an array substrate of an LCD panel in accordance with thethird embodiment of the present invention.

FIG. 11 is a schematic diagram illustrating a method of repairing adefect in an array substrate of an LCD panel in accordance with thefourth embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIGS. 3-8. FIGS. 3-8 are schematic diagrams illustratinga method of repairing a defect in an array substrate of an LCD panel inaccordance with the first embodiment of the present invention. FIGS. 3,5 and 7 are top views of the array substrate, FIG. 4 including FIG. 4 aand FIG. 4 b are cross-sectional views of the array substrate shown inFIG. 3 along a line AA′, FIG. 6 is a cross-sectional view of the arraysubstrate shown in FIG. 5 along a line BB′, and FIG. 8 is across-sectional view of the array substrate shown in FIG. 7 along a lineCC′. As shown in FIG. 3 and FIG. 4, an array substrate 30 is provided.The array substrate 30 includes a plurality of scan lines 32 arranged inparallel, a plurality of data lines 34 arranged perpendicular to thescan lines 32 disposed over the array substrate 30, a plurality of pixelregions 36 defined by the scan lines 32 and the data lines 34, aplurality of thin film transistors 38 disposed in each pixel region 36,and a plurality of common lines 40 arranged in alternately with the scanlines 32. The common lines 40 and the scan lines 32 are formed by thesame lithography process, and the common lines 40 and the scan lines 32are normally referred to as metal 1 (M1). The data lines 34 are formedsubsequent to the scan lines 32, and the data lines 34 are thereforeusually referred to as metal 2 (M2). The array substrate 30 furtherincludes a plurality of pixel electrodes 42 disposed in each pixelregion 36, and electrically connected to the source/drain of each thinfilm transistor 38 via a through hole D. As FIG. 4 shows, the arraysubstrate 30 also has an intermediary layer including a dielectric layer44 and a passivation layer 46 disposed between the common lines 40 andthe pixel electrodes 42. It is noted that the array substrate 30 furtherincludes a connecting bridge 34 a (as shown in FIG. 3 and FIG. 4) ineach pixel region 36 in case of repairing requirement. The connectingbridge 34 a is formed in the M2 layer, and the function of theconnecting bridge 34 a will be detailed in following description.

This embodiment illustrates a Cst on common type LCD, and thus a portionof each pixel electrode 42 overlaps each of the common line 40 in eachpixel region 36 to form a storage capacitor region. In the storagecapacitor region, the common line 40 and the pixel electrode 42respectively serve as a bottom electrode and an upper electrode of thestorage capacitor, and the dielectric layer 44 and the passivation layer46 serve as a capacitor dielectric layer so as to from a storagecapacitor in each pixel region 36.

However, in the manufacture process of the array substrate, due tounexpected reasons, defects may occur in the storage capacitor region.As shown in FIG. 3, FIG. 4 and FIG. 5, if a defect 48, such as aparticle defect (as shown in FIG. 4 a) or a loss of portion of thedielectric layer 44 and a loss of portion of the passivation layer 46(as shown in FIG. 4 b), unexpectedly occurs to the storage capacitorregion in one of the pixel region 36, the pixel region 36 will fail. Inthis embodiment, whether the defect 48 is the particle defect (shown inFIG. 4 a) or the loss defect (shown in FIG. 4 b), the pixel electrode 42and the common line 40 are electrically connected, thereby forming ashort-circuitry. But it is noted that, the method of the presentinvention which will be described as following can be not only appliedto the situation that the defect 48 must make pixel electrode 42 andcommon line 40 be short-circuited but also the situation that the defect48 just makes the storage capacitor malfunction or work non-normally.

Taking the loss defect (shown in FIG. 4 b) for example, when the defect48 is detected, the pixel region 36 having the defect 48 needs to berepaired. As shown in FIGS. 5 and 6, a cutting process is performedalong and near the both two sides of the common line (as the cuttinglines 47 shown in FIG. 5 and FIG. 6) to divide the pixel electrode 42having the defect 48 into a first portion 421 substantiallycorresponding to the common line 40, a second portion 422, and a thirdportion 423, not connecting to each other. In this embodiment, thecutting process is a laser cutting process, but not limited. Inaddition, the cutting depth is not limited to the pixel electrode 42,and can be deeper, even can reach the upper surface of the arraysubstrate 30 (as shown in the FIG. 6). To ensure the electricaldisconnection of the pixel electrode 42 and the common line 40, thepassivation layer 46 or the dielectric layer 44 can be cut along withthe pixel electrode 42 in the cutting process. It is appreciated thatthe cutting line is along both sides of the common line 40, but thecutting line should not be too close to the sides of the common line 40for preventing the electrical connection between the pixel electrode 42and the common line 40 through the cutting line. After the cuttingprocess, the pixel electrode 42 is divided into three portions, and thefirst portion 421 having the defect 48 is isolated from the secondportion 422 and the third portion 423.

Sequentially, as shown in FIGS. 7 and 8, the second portion 422 of thepixel electrode 42 is electrically connected to the gate electrode 35 ofthe scan lines 32 through welding the source/drain electrode 37 and thegate electrode 35 together at the point E, and the third portion 423 ofthe pixel electrode 42 is electrically connected to another scan lines32 through respectively welding the connecting bridge 34 a and the pixelelectrode 42 together at the point F as well as welding the connectingbridge 34 a and the another gate line 32 together at the point G. Inthis embodiment, the electrical connection between the second portion422 and the gate electrode 35, and between the third portion 423 andanother scan line 32 is achieved by laser welding, but not limited. Asshown in FIGS. 7 and 8, the source/drain 37 which electrically contactswith the pixel electrode 42 via the through hole D overlaps the gateelectrode 35 of the thin film transistor 38, and thus the source/drain37 and the gate electrode 35 can be directly welded as shown in FIG. 8.On the other hand, the third portion 423 and another scan line 32 arenot overlapping. In such a case, the connecting bridge 34 a, which ispart of the M2 layer, and interposed between the third portion 423 andthe scan line 32, serves as a connecting media between the third portion423 and the scan line 32 as shown in FIG. 8. Therefore, the thirdportion 423 can be connected to the scan line 32 by welding through theconnecting bridge 34 a. Since the second portion 422 and the thirdportion 423 are respectively connected to the scan lines 32 and arerespectively provided a voltage of the scan line 32, voltage differenceswill respectively exist between the second portion 422 and the commonelectrode of the CF substrate (not shown) as well as between the thirdportion 423 and the common electrode. Consequently, the bright dotdefect is eliminated while displaying in case the LCD is NW type. It isappreciated that although there is no voltage difference between thefirst portion 421 and the common electrode, back light will be shaded bythe common line 40. Thus, bright dot defect in the first portion 421will also be eliminated.

Please refer to FIG. 9. FIG. 9 is a schematic diagram illustrating amethod of repairing a defect in an array substrate of an LCD panel inaccordance with the second embodiment of the present invention. Thisembodiment also illustrates a Cst on common type LCD similar to thefirst embodiment, thus like elements are denoted by like numerals, andare not detailed redundantly. As shown in FIG. 9, an array substrate 30is provided, and a defect 48 unexpectedly appears. Different from thefirst embodiment is that the defect 48 in the second embodiment is acommon line loss or breakage. Usually, a common line loss, as shown inFIG. 9, makes the common line break and have two broken side portions,the first broken side portion 401 and the second broken side portion402. The common line loss or breakage not only leads to failure of thestorage capacitor of the pixel region 36 having the defect 48, but alsofailure of all the pixel regions 36 using the same common line 40.

Then, a cutting process is then performed to divide the pixel electrode42 having the defect 48 into a first portion 421 substantiallycorresponding to the common line 40 and including the defect 48, asecond portion 422, and a third portion 423 not connecting to eachother. The first portion 421 also has two portions corresponding to andoverlapping the two broken side portions 401 and 402 of the common line40. Subsequently, the second portion 422 is electrically connected tothe scan line 32, and the third portion 423 is electrically connected toanother scan line 32 through the connecting bridge 34 a by laserwelding, for instance. In addition, the first portion 421 of the pixelelectrode 42 is electrically connected to the broken common line 40through respectively welding the broken common line 40 and the firstportion 421 together at the point H of the first broken side portion 401and at the point I of the second broken side portion 402.

In this embodiment, the first portion 421 of the pixel electrode 42 isisolated from the second portion 422 and the third portion 423 in thecutting process, and electrically connected to the common line 40through the laser welding process. The electrical connection of thefirst portion 421 and the common line 40 enables the first portion 421to serve as a substitute circuit. Accordingly, the bright dot defect iseliminated by electrically connecting the second portion 422 and thethird portion 423 to the corresponding scan lines 32, and the commonline loss is repaired by electrically connecting the broken common line40 with the first portion 421.

Please refer to FIG. 10. FIG. 10 is a schematic diagram illustrating amethod of repairing a defect in an array substrate of an LCD panel inaccordance with the third embodiment of the present invention. As shownin FIG. 10, the array substrate 50 includes a plurality of scan lines 52arranged in parallel, a plurality of data lines 54 arrangedperpendicular to the scan lines 52 disposed over the array substrate 50,a plurality of pixel regions 56 defined by the scan lines 52 and thedata lines 54, a plurality of thin film transistors 58 disposed in eachpixel region 56, and a plurality of pixel electrodes 62 disposed in eachpixel region 56 and electrically connected to the source/drain of eachthin film transistor 58. Different from the above embodiments, thisembodiment illustrates a Cst on gate type LCD, and thus an auxiliaryelectrode 64 which is made of M2 and electrically contacts the pixelelectrode 62 via a through hole J and overlaps the scan line 52.

The auxiliary electrode 64 disposed between the pixel electrode 62 andthe scan line 52 in each pixel region 56 and is electrically connectedto the corresponding pixel electrode 62. Therefore, the pixel electrode62 and the auxiliary electrode 64 serve as an upper electrode of thestorage capacitor, and a portion of the scan line 52 serves as a bottomelectrode.

In a normal case, the auxiliary electrode 64 is not electricallyconnected to the data line 54. However, due to some unexpected factorsin the manufacture process of array substrate, the auxiliary electrode64 and the data line 54 may be short-circuited, thereby forming a defect66 known as M2 residue as shown in FIG. 10. Since the auxiliaryelectrode 64 is electrically connected to the pixel electrode 62, theshort-circuitry between the auxiliary electrode 64 and the data line 54will cause failure of the pixel region 56.

In this embodiment, a cutting process e.g. a laser cutting process isperformed to divide the pixel electrode 62 into a first portion 621having the defect 66, and a second portion 622 not connecting to eachother. Subsequently, the second portion 622 is electrically connected tothe scan line 52 by laser welding at point K, for instance. Since thefirst portion 621 having the defect 66 is isolated from the secondportion 622, and the second portion 622 is electrically connected to thescan line 52, a voltage difference will exist between the second portion622 of the pixel electrode 62 and the common electrode of the CFsubstrate (not shown) and the effect of the defect 66 can be eliminated.

Please refer to FIG. 11. FIG. 11 is a schematic diagram illustrating amethod of repairing a defect in an array substrate of an LCD panel inaccordance with the fourth embodiment of the present invention. Thisembodiment also illustrates a Cst on common type LCD similar to thefirst embodiment, thus like elements are denoted by like numerals, andare not detailed redundantly. As shown in FIG. 11, an array substrate 30is provided. The array substrate 30 includes a defect 48 in the storagecapacitor region. For instance, as the previous mentioned, the defect 48may be a dielectric layer loss or a particle that causes ashort-circuitry between the pixel electrode 42 and the common line 40.It is appreciated that the array substrate 30 of this embodiment doesnot include a connecting bridge disposed in each pixel region 36.

Subsequently, a cutting process is performed to divide the pixelelectrode 42 having the defect 48 into a first portion 421 including thedefect 48, and a second portion 422 which is substantially like aU-shaped structure, not connecting to each other. In the cuttingprocess, please note that the common line 40 is also cut so that onesection of the common line 40 having the defect 48 is isolated fromother sections of the common line 40.

Following that, the first portion 421 of the pixel electrode 42 iselectrically connected to one of the scan lines 32 through welding at apoint L, and the second portion 422 of the pixel electrode 42 iselectrically connected to the common line 40 corresponding to the secondportion 422 through respectively welding at both two sides of the secondportion 422 corresponding to the two terminals of the U-shapedstructure, such as at the points M and N. In this embodiment, the firstportion 421 of the pixel electrode 42, which is isolated from the secondportion 422, is electrically connected to the scan line 32 to eliminatethe bright dot defect. On the other hand, the second portion 422 iselectrically connected to the common line 40 and serves as a substitutecircuit of the section of the common line 40 having the defect 48.Consequently, the pixel regions 36 using the same common line 40 canoperate normally.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method of repairing a defect in a liquid crystal display panelcomprising: providing an array substrate comprising: a plurality of scanlines and data lines disposed over said array substrate and togetherdefining a plurality of pixel regions, and at least one of said pixelregions comprising a transistor, a pixel electrode electricallyconnected to a source/drain electrode of said transistor, a storagecapacitor having an upper electrode and a bottom electrode, wherein saidpixel electrode is electrically coupled to said storage capacitor; and adefect positioned in said storage capacitor; performing a cuttingprocess to divide said pixel electrode into a first portion and a secondportion not connecting to each other, wherein said first portion of saidpixel electrode is corresponding to said storage capacitor having saiddefect; and electrically connecting said second portion of said pixelelectrode to one of said scan lines.
 2. The method of claim 1, whereineach said bottom electrode is a portion of one of said scan lines andsaid upper electrode is electrically coupled to said pixel electrode. 3.The method of claim 2, wherein each said upper electrode is made of amaterial which is the same as that of said data line.
 4. The method ofclaim 3, wherein said defect is a metal residue which makes said upperelectrode electrically connect to one of said data lines.
 5. The methodof claim 1, wherein said array substrate further comprises a pluralityof common lines and each said bottom electrode is a portion of one ofsaid common lines and each said upper electrode is a portion of saidpixel electrode.
 6. The method of claim 5, wherein said defect is acommon line loss in one of said common lines.
 7. The method of claim 6,wherein said cutting process further comprises dividing the pixelelectrode into a third portion not connecting to the first portion orthe second portion, and electrically connecting said third portion toanother said scan line, and electrically connecting said first portionto said one of said common lines having said common line loss.
 8. Themethod of claim 7, wherein said pixel region further comprises aconnecting bridge, and the step of connecting said third portion to saidanother said scan line is performed through electrically connecting saidthird portion to said connecting bridge and connecting said connectingbridge to said another said scan line.
 9. The method of claim 7, whereinsaid one of said common line has two broken side portions, the firstbroken side portion and the second broken side portion and the step ofconnecting said first portion to said one of said common lines isperformed through respectively welding said one of said common line andsaid first portion together at the first broken side portion and at thesecond broken side portion.
 10. The method of claim 5, wherein saidcutting process further comprises dividing said pixel electrode into athird portion not connecting to said first portion and said secondportion, and electrically connecting said third portion to another saidscan line.
 11. The method of claim 10, wherein said cutting process isperformed through cutting said pixel electrode along both two sides ofsaid common line to divide said pixel electrode into said first portion,said second portion and said third portion.
 12. The method of claim 10,wherein said pixel region further comprises a connecting bridge, and thestep of connecting said third portion to said another said scan line isperformed through electrically connecting said third portion to saidconnecting bridge and connecting said connecting bridge to said anothersaid scan line.
 13. The method of claim 10, wherein the step ofelectrically connecting said third portion to another said scan line isperformed by laser welding.
 14. The method of claim 1, wherein saidstorage capacitor further comprises an intermediary layer interposedbetween said upper electrode and said bottom electrode, and said defectis a particle in said intermediary or a loss of said intermediary layer.15. The method of claim 14, wherein said defect leads to a shortcircuitry between said upper electrode and said bottom electrode. 16.The method of claim 14, wherein said intermediary layer is cut alongwith said pixel electrode in said cutting process.
 17. The method ofclaim 14, wherein said intermediary layer comprises a passivation layerand a dielectric layer.
 18. The method of claim 17, wherein saidpassivation layer is cut along with said pixel electrode in said cuttingprocess.
 19. The method of claim 17, wherein said dielectric layer iscut along with said pixel electrode and said passivation layer in saidcutting process.
 20. The method of claim 1, wherein said cutting processis a laser cutting process.
 21. The method of claim 1, wherein the stepof connecting said second portion of said pixel electrode to one of saidscan lines is performed by laser welding.
 22. The method of claim 1,wherein the step of connecting said second portion of said pixelelectrode to one of said scan lines is performed through electricallyconnecting the source/drain electrode and said one of said scan lines bywelding.
 23. A liquid crystal display panel, comprising: an arraysubstrate; a plurality of scan lines and data lines disposed over saidarray substrate and together defining a plurality of pixel regions, andat least one of said pixel regions comprising a transistor, a pixelelectrode electrically connected to a source/drain electrode of saidtransistor, a storage capacitor having an upper electrode and a bottomelectrode, wherein said pixel electrode is electrically coupled to saidstorage capacitor; and a defect positioned in said storage capacitor;wherein said pixel electrode comprises a first portion which iscorresponding to said storage capacitor including said defect, and asecond portion not connecting to each other; and wherein said secondportion of said pixel electrode is electrically connected to one of saidscan lines.
 24. The liquid crystal display panel of claim 23, whereineach of said bottom electrode is a portion of one of said scan lines andsaid upper electrode is coupled to said pixel electrode.
 25. The liquidcrystal display panel of claim 24, wherein said upper electrode is madeof a material which is the same as that of said data line.
 26. Theliquid crystal display panel of claim 25, wherein said defect is a metalresidue which makes said upper electrode electrically connect to one ofsaid data lines.
 27. The liquid crystal display panel of claim 23,wherein said array substrate further comprises a plurality of commonlines and each said bottom electrode is a portion of one of said commonlines and each said upper electrode is a portion of said pixelelectrode.
 28. The liquid crystal display panel of claim 27, whereinsaid defect is a common line loss in one of said common lines.
 29. Theliquid crystal display panel of claim 28, wherein said pixel electrodefurther comprises a third portion not connecting to said first portionand said second portion, and said third portion is electricallyconnected to another said scan line, and said first portion iselectrically connected to said one of said common lines.
 30. The liquidcrystal display panel of claim 27, wherein said pixel electrode furthercomprises a third portion not connecting to said first portion and saidsecond portion, and said third portion is electrically connected toanother said scan line.
 31. The liquid crystal display panel of claim27, wherein said pixel region further comprises a connecting bridge, andthe connection of said third portion and said another said scan line isvia an electrical connection between said third portion and saidconnecting bridge and an electrical connection between said connectingbridge and said another said scan line.
 32. The liquid crystal displaypanel of claim 23, wherein said storage capacitor further comprises anintermediary layer interposed between said upper electrode and saidbottom electrode, and said defect is a particle in said intermediary ora loss of said intermediary layer.
 33. The liquid crystal display panelof claim 32, wherein said defect leads to a short circuitry between saidupper electrode and said bottom electrode.
 34. The liquid crystaldisplay panel of claim 23, wherein the electrical connection betweensaid second portion and said one of said scan lines is via an electricalconnection between the source/drain and said one of said scan lines.